Explosive attacks are a major terrorist threat that is increasing day by day. Honeycomb sandwich panels have a high capacity to absorb energy under blast loads and are very popular for protective structures against blast. Honeycomb sandwich panels are designed with various design parameters. The investigation of the blast mitigation performance of the sandwich panels through experiments is very costly as well as a hazard for both the environment and people. However, in this present work, the blast performance of the square honeycomb sandwich panels (SHSPs) was investigated numerically by dynamic explicit analysis using ABAQUS 6.14. The SHSPs with equal or unequal mass were modelled with 51 mm, 61 mm, and 71 mm core heights to analyse their effects on the face sheet deflection and energy absorption. The blast resistance characterization was carried out at 1 kg to 3 kg of trinitrotoluene (TNT) explosion for a 0.1 m stand-off distance after the mesh convergence and validation study. The simulation results show that increasing the core height improved blast resistance by reducing back face deflection and increasing energy absorption by the core. The SHSPs with a 71 mm core height outperform the other modelled sandwich panels and can be utilized for armoured applications.